Method of sharpening files



July 18, 1944. I MARTlNEs 2,353,683

METHOD OF SHARPENING FILES Filed Aug. 30, 1943 min ATTORNEYS PatentedJuly 18, 1944 UNITED STATES PATENT. ()F' F'ICE METHOD OF snARPENINGFILES Rene Martines, Cranston, R. I. v Application August 1943, SerialNo. 500,465

2 Claims.

This invention relates to a method and apparatus for the sharpening offiles.

,File teeth are usually formed by a chisel cutting action which raises atooth and provides an arcuate surface along the tooth adjacent itspoint. The teeth become dull by a wearing off of the point and some ofarcuate surface. Files are sometimes attempted to be resharpened byetching or sandblasting but these methods are not entirely satisfactoryas the original shape of the tooth is not restored.

One of the objects of this invention is to resharpen the file byrestoring to each of the teeth the original shape that these teeth havewhen formed new by a chisel action.

Another object of this invention is to grind the worm arcuate surfaceadjacent the point of the tooth so as to cause this arcuate surface torun to a sharp point adjacent the surface with reference to which it isdisposed at an angle.

Another object of this invention is to wipe abrasive material along thisarcuate surface until this surface is worn back to the shape desired anda sharp point provided on the file tooth.

Another object of this invention is to wipe this v surface with aresilient element which will apply an abrasive cutting material thereto.

With these and other objects in view, the invention consists of certainnovel features of construction, as will be more fully described andparticularly pointed out in the appended claims.

In the accompanying drawing:

Fig. l is a sectional view illustrating the file resharpening apparatusand showing a file in po'- sition with reference thereto; I

Fig, 2 is a fragmental view showing in section and on a larger scale aportion of the cutting wheel and the file in its position with referencethereto;

Fig. 3 is a fragmental section illustrating similar to Fig. 2 but on agreatly enlarged scale;

Fig. 4 is a sectional view on substantially line 4--4 of Fig. 1;

Fig. 5 is a top plan view of the structure shown in Fig. 1 with partsbroken away;

Fig. 6 is a diagrammatic illustration of a modified form of theinvention.

In proceeding with this invention I provide resilient elements such asflexible wires for applying an abrasive cutting material to the teeth ofa file.

' the drum '55.

elements I'B which may be conveniently supplied by attaching cardclothing consisting of a fabric back ll to support these flexibleelements 16 to The length and gage of the wire which is used will varydepending somewhat upon the size of the file which is to be ground. Forexample No. 35 wire is adequate for files with cuts from No. 1 to No, 6while No. 31 wire is better for coarser files.

A sump i8 is provided below the drum [5 which sump contains oil andemery or a, suitable cutting compound designated generally IS. Theflexible element or wires I6 dip into this cutting compound and becomecoated with the cutting compound lifting it upwardly to apply thecompound to any surface with which it may come in contact.

A guard 20 extends from the rear of the stand Ii! arcuately forward asshown in Fig. 1 while a second guard 2i extends upwardly to cover thefront side of the drum.

Upon the front side of the apparatus I provide a file supporting standwhich consists of an arm 22 pivoted as at 23 to the forward supportingsurface 24 while at the other end of this arm a post 25 is swivellymounted as at 26 and supports a horizontal rod 2'! upon which a carrier28 is mounted having a. plurality of rods 29 therein each equipped witha chuck 3!] for the holding of a file 3!. A spring 32 tends to swing thecarrier 28 about the horizontal rod 21 as a pivot to cause the file 3|to move into engagement with the flexible elements l6 carried by thedrum. The carrier 28 may be swung to and from the rotating drum bymovement of the arm 22 along the arc having a radius 32 while thecarriage may also be swung about the arc whose radius is 33 from thecenter of the post 25 which also pivotally mounts the carrier 28, Thusthe position of the files with reference to the drum may be convenientlyde-' termined.

The mill cut file 3! is formed by a chisel which provides a recess 35(see Fig. 3) and at the same time forms the abrupt surface 31 andarcuate surface 38 while a secondary inclination 39 is also formed. Thefile teeth thus each designated generally 40 are provided with a sharppoint 41 by reason of the junction of the surfaces 31 and 38. It is thispoint which becomes worn to cause the file to become dull and it isdesired to restore this point in resharpening the file which Iaccomplish with the apparatus heretofore described. The

file 3| is disposed substantially as shown in Fig. 1

wardly into the recess 35 so as to engage the next 7 tooth. As each ofthe elements wipe across the surface 38 they conform to the shape of thesurface and wear back this surface so that the shape of the tooth byreason of this surface joining the surface 31 remains substantially thesame or is resharpened to substantially the same shape as the tooth wasprior to becoming dull. Thus the shape of, the tooth as it originallyoccurred is restored by the grinding back of this tooth along this longsurface which forms the angle of the point of the tooth. y

It is not essential that the flexible element l5 extend from a rotarydrum and I have illustrated in Fig. 6 these elements as mounted in abelttype 45 extending over the two pulleys or drums 46 while there is asupporting shelf '41 over which the belt 45 extends. By reason'of thiselongated extent 48 above thisshelf 4'! a larger portion of a filelengthwise thereof may be sharpened at one time than where thesharpening occurs over a cylindrical portion having a short tangentialextent engaged by the file.

After the files have been ground to restore the shape of their teeth soas to provide a sharp point the files may be pickled to further shapeand also to give them the appearance of a new file where such isdesired.

The flexibility of the elements I6 is such that files of various shapesmay be resharpened, such for instance as flat, half-round or round, aswell as dental burrs and the like. 1

I claim:

1. The method of sharpening a mill cut file comprising the steps ofapplying a rotary, wire bristled brush having abrasive upon the bristlesthereof to the teeth of a file in such a manner that the abrasivebearing bristles travel in an arcuate path from the back of the teethtoward the cutting edges thereof thereby imparting an arcuate surfaceupon the back of the teeth and extending to the cutting edges thereofand thereby renewing the sharpness of the cutting edges.

2. The method of sharpening a mill cut file comprising the steps ofapplying a flexible bristled brush having abrasive upon the bristlesthereof to the teeth of a file in such a manner that the abrasivebearing bristles are flexed and travel from the back of the teeth towardthe cutting edges thereof thereby imparting an arcuate surface upon theback of the teeth and extending to the cutting edges thereof and therebyrenewing the sharpness of the cutting edges.

RENE MAR'I'INES.

